ANALYSIS OF THE STRUCTURAL PROTEIN GENE SEQUENCE SHOWS KYASANUR-FOREST-DISEASE VIRUS AS A DISTINCT MEMBER IN THE TICK-BORNE ENCEPHALITIS-VIRUS SEROCOMPLEX

Kyasanur Forest disease (KFD) virus is a highly pathogenic member of t he family Flaviviridae producing a haemorrhagic disease in infected hu man beings. Despite this high pathogenicity and potential epidemiologi cal importance, there have been relatively few detailed antigenic or m olecular studies on KFD virus. The nucleotide sequences of the genes e ncoding the structural proteins of the virus have now been determined. From these data we conclude that KFD virus is a distinct member in th e tick-borne flavivirus complex with characteristic protease cleavage sites, fusion peptide, signal sequences and hydrophobic transmembrane domains. Comparison of the deduced amino acid sequences of KFD virus s howed close relationships with other tick-borne flaviviruses. Among th e structural proteins, the E protein showed maximum similarity (77.4 % to 81.3 %) to tick-borne flaviviruses. Alignment of the amino acid se quence with those of other known tick-borne flaviviruses revealed many conserved regions confirming its identity as a member of the tick-bor ne encephalitis group, although the genetic marker EHLPTA showed a T - -> K substitution in KFD virus. The proposed genetic marker at amino a cid positions 232 to 234 (AQE) was unique for KFD virus. A dendrogram derived from the amino acid alignment showed a phylogenetic relationsh ip similar to those obtained on the basis of serological studies. The question of the sudden emergence of KFD virus in India and the possibi lities of developing recombinant virus vaccines are discussed.